Many of you are, unlike me, far too young to remember the Rio Earth Summit of 1992-indeed many of you were probably-almost certainly-yet to be born.

But in so many ways what happened nearly 20 years ago has brought us all together here today in this wonderful City Forest of Bandung, Java.

For in 1992 the leaders of the world, civil society, businessmen and woman, youth leaders and children just like you and from across the globe came together with a sense of purpose, a vision and some really smart ideas to make this a better world.

They forged something called Agenda 21-think global, act local.

They established some of these big treaties on issues ranging from global warming to the concern over biodiversity-the loss of animals, plants and other living things.

They basically gave substance to what we call sustainable development-the glue that binds this meeting, the issue that has brought us together and the hope for this and future generations.

Next year in the same city in Brazil, world leaders, civil society, business men and woman, youth leaders and children will come together again-20 year after the Earth Summit-for Rio+20.

Why?

Because everyone who met in 1992 was wrong or they failed? No.

But because the size of the problem we are facing just keeps getting bigger-bigger perhaps than a previous generation ever imagined.

And because the world has changed in ways that in 1992 were unimaginable-or at best merely glimpsed.

Sometime on or around the 31st of October a baby will be born that will put the global human population at seven billion-in 1992 there were around 5.5 billion people.

It is not so much the numbers as the way in which we are consuming-the way in which we are gobbling up our fish and our forests in ways that could mean by 2050, in the life time of many young people in this room, the world could triple its consumption.

Next month UNEP will release a small booklet of what we call indicators as part of our flagship Global Environmental Outlook series.

Some of the areas it is likely to spotlight.

Carbon dioxide, linked with activities such as driving around in cars or lighting our homes, has increased by close to 10 per cent since 1992-average global temperatures have risen by 0.4 degrees C over the same period

The area of forests has decreased by 300 million hectares since the early 1990s-an area the size of country like Argentina.

Today over half of all the world's fish stocks are fully exploited, up from 13 per cent in 1992

And there are lots of other trends.

Land degradation now affects perhaps a quarter of the Earth's surface to varying extents, and has been growing by maybe around one per cent a year since the 1980s

Populations of fish and freshwater vertebrates have declined on average by nearly 50 per cent since 1987 as compared with an around 30 per cent decline for terrestrial and marine species.

But some indicators have moved in a more positive direction.

Protected areas have for example grown from around 8.6 per cent in 1992 to over 12 per cent

In 2010, $211 billion was invested in renewable energy-more than in oil, coal or other fossil fuels.

The high flying ozone layer, which protects us all from deadly ultra violet rays, is recovering as a result of the cutting of the substances or gases that were killing it.

So how do we manage up the positives and manage down the negative developments.

How do we take the extraordinary transitions happening in your schools, homes, communities and countries and scale them up, accelerate them into what we at UNEP call a Green Economy.

How do we trigger growth and development in a way that delivers decent green jobs that will allow you to reach your potential without seven billion people, rising to over nine billion by 2050, pushing the planet beyond key thresholds and limits-

Because with 1.3 billion people unemployed or underemployed and half a billion young people joining the workforce looking for employment in less than ten years, we need economic development everywhere.

That is the challenge for Rio+20 and that is the challenge for you young people here this week.

Because what you decide, and what you put in the Bandung Declaration at the end of your meeting here, is your input to a global effort currently underway.

On November 1, at the UN's headquarters in New York, governments, businessmen and woman, civil society and others will express what they want from this Rio+20 meeting.

That input would be incomplete and would fall short if the next generation of leaders-that's you and you-do not deliver a clear and concrete view of what you want and hope for next June in Rio.

20 years may seem a lifetime away-I can tell you as an adult it only seems like yesterday.

The world cannot wait another 20 years for a meaningful and game-changing response to the changes now emerging on planet Earth-it has to be now.

Thank you for coming to the UNEP Tunza International Children and Youth Conference-enjoy this week in this wonderful city and country.

Thanks too to our remarkable hosts who have themselves set out on an exciting journey to discover new ways of managing their forests to delivering youth employment within a Green Economy.

Yesterday the world lost one of the iconic figures of the environmental movement, Wangari Maathai.

If you did not know her, then let me simply say that as initially a Kenyan and then a global campaigner, Wangari understood the inescapable and increasingly relevant link between environmental sustainability and peace-and in doing so won the Noble Peace Prize in 2004.

In 1992, the year of the Earth Summit she was brutally attacked by riot police along with other women trying to defend her country's forests-a measure of her courage.

That same year a young 12 year-old girl called Severn Suzuki also showed courage when she stood up for the environment.

She delivered a speech to the Earth Summit that humbled and silenced the world and has become a legend on YouTube.

In an interview on UNEP's web site which you can read Severn, now a mum and aged 32 years-old, sent a message to this meeting here in Bandung that I want to share.

"I think (the speech) it's still so popular because it speaks to the need for - and the power of - the voice of youth. Adults need to be reminded of the consequences of their actions, even though they have multiple interests and ulterior motives".

"Young people see things for what they are and call their elders on their actions. Youth don't know what isn't possible," she said.

That is as true today as it was in 1992

Children and Youth are currently meeting in Bandung, Indonesia to deliver a clear and concrete view of what they want and hope for next June in Rio